The invention relates to a control arrangement for infinitely variable traction roller transmissions in which power is transmitted through pivotally supported traction rollers whose transmission ratio determining pivot position may be varied by hydraulic mechanisms.
The forces required for th engagement of the various traction surfaces are generally very large and are therefore supplied in many cases by high pressure fluid systems. However, such high pressure fluid systems are expensive and furthermore subject to frequent leakages since the seal rings needed in the high pressure system are subjected to high loads.
Mechanical operating mechanisms have therefore been utilized but naturally while such mechanical operating mechanisms are good for smaller transmissions they are generally not satisfactory for larger power transmissions. A good mechanical transimssion ratio control arrangement is for example shown in applicant's U.S. application Ser. No. 259,043 of Oct. 17, 1988 entitled "Infinitely Variable Traction Roller Transmission". This arrangement is also simple and inexpensive but for high power transmissions and automatic ratio change as it is, for example, required for automotive applications, a purely mechanical arrangement is not adequate.
It is therefore the principal object of the present invention to provide a control system for a traction roller transmission of the type disclosed in U.S. application Ser. No. 259,043 which is suitable for high power transmission requirements but which is relatively simple and without the operating problems caused by high pressure hydraulic pumps and operating mechanisms.